1. Field of the Invention
The invention is directed to a biopsy assembly for an x-ray examination apparatus having an x-radiator with a focus from which a ray pyramid emanates, and a radiation receiver arranged lying opposite thereto for generating an x-ray picture of an examination subject situated between the two.
2. Description of the Prior Art
Devices are known for the identification of a paracentesis point for a biopsy needle pertaining to a diagnostically relevant region imaged on the x-ray picture and situated within the examination subject. Such devices have a guide element for aligning the biopsy needle to the paracentesis point having a channel for the biopsy needle whose diameter essentially corresponds to that of the biopsy needle, and means for positioning the guide element relative to the examination subject.
A biopsy assembly for mammography is known from the advertising brochure of Siemens AG, "Der moderne Mammographie-Arbeitsplatz: MAMMOMAT B", Order number, A19100-M1087-A789-01. The known biopsy assembly has two scales describing an angle and being imagable on the x-ray picture. The scales are attached to a plate for compression of the examination subject. The scales are applied to the edge of an opening provided in the plate, the examination subject being accessible through this opening. Means are also provided that allow a shadow cross whose legs proceed parallel to the scales to be projected onto the examination subject. The legs of the shadow cross have a length such that they intersect the scales. The shadow cross is adjustable such that the position of the intersection of its legs can assume and arbitrary position on the region of the examination subjection accessible through the opening of the plate.
When an x-ray picture of the examination subject is prepared, the scales are imaged together with the examination subject. When the x-ray picture exhibits a diagnostically relevant region within the examination subject that is to be punctured or to be marked for a test, the coordinates of the region are determined on the x-ray picture with reference to the scales. Subsequently, the shadow cross is set to corresponding coordinates for determining the paracentesis point for the biopsy needle. For puncturing or marking, an incision is then made with the biopsy needle at the intersection of the legs of the shadow cross and the biopsy needle is advanced into the required depth. The paracentesis point identified in this way lies on a straight line that proceeds through the diagnostically relevant subject and through the focus of the x-radiator. The examination subject is not to be moved in the time span between the production of the x-ray picture and the execution of the puncture.
The known biopsy means is constructed in a very simple way and allows the paracentesis point for the biopsy needle to be determined with great precision with reference to a single x-ray picture, however, when the diagnostically relevant region is situated far inside of the examination subject, a risk exists that the biopsy needle will be conducted past the region. When this is not noticed, there is a risk of misdiagnosis. At the very least, the puncturing must be repeated, this being extremely uncomfortable for the patient.
This disadvantage is avoided in a biopsy assembly as disclosed in European Application 0 146 511. This biopsy assembly has means for the determination of a paracentesis point for the biopsy needle pertaining to a diagnostically relevant region, by a calculating operation with reference to two x-ray pictures exposed at different angles on which a stationary mark is imaged in addition to the diagnostically relevant region. This paracentesis point lies on a straight line that proceeds through the diagnostically relevant region and proceeds perpendicularly to the surface of a planar support for the examination subject. The known biopsy assembly also has a guide device for the biopsy needle with a channel whose longitudinal axis proceeds at a right angle relative to the surface of the support for the examination subject. Means for positioning the guide device are also provided with which the guide device is adjustable in the direction of the three spatial axes. For executing a puncture, the guide device is positioned such that the longitudinal axis of its channel proceeds through the identified paracentesis point and thus through the diagnostically relevant region. Although this makes it impossible for the biopsy needle to be conducted past the diagnostically relevant object, two x-ray pictures are required for the determination of the paracentesis point for the biopsy needle, resulting in an undesirable high radiation load on the examination subject. Further, the known x-ray device is constructed in a complicated fashion.